Various coordinate locating devices are known for locating the coordinates of an object. Some coordinate locating devices can detect the coordinates of an object from a pointing instrument, such as a pen, a fingertip, or a specific device dedicated for use with such devices. Accordingly, a user can input information by the pointing instrument.
Common techniques employed in conventional coordinate locating devices for locating the coordinates of an object include mechanical buttons, crossed light beams, acoustic surface waves, capacitance sensing, and resistive materials. Among these techniques, those employing crossed light beams are not limited by the display panel size and are therefore cost competitive.
For example, Griffin, U.S. Pat. No. 4,820,050 discloses a solid-state optical position determining apparatus having an LED light source and an image sensor. However, the apparatus can only locate the coordinates of a single object, resulting in undesirably limited applications.
Another example is an apparatus disclosed by Segen, U.S. Pat. No. 5,484,966, entitled “sensing stylus position using single 1-D image sensor.” The apparatus utilizes two mirrors and one image sensor, but can also locate the coordinates of a single object.
Surpassing the above two conventional techniques, US Patent Publication. No. 2009/0,066,662 by Liu, Yun-Cheng, et al. proposed a system capable of distinguishing multiple touch points, and US Patent Publication. No. 2008/0143682 by Shim, Yeon Shim, et al. also proposed a display device having a multi-touch recognition function. However, in the proposals, at least three image sensors are required, respectively, thus greatly increasing manufacturing costs.